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Caption

Streptococcus pneumoniae. Coloured Transmission Electron Micrograph (TEM) of a section through a pair of Streptococcus pneumoniae bacteria. These Gram-positive spherical (coccoid) bacteria are usually found in pairs, as here, but do form short chains or clusters. The cell wall is visible with inner cell contents appearing granular, coloured red & white. An orange capsule surrounds the cells and this is associated with certain pathogenic states. S.pneumoniae occurs both as a healthy commensal and a pathogen in the human respiratory tract. If pathogenic, it causes pneumonia, pleurisy, peritonitis and meningitis. Magnification: x18,000 at 35mm size.